The present invention relates to a scientific computing machine and, in particular, to a logarithmic function arithmetic unit for use in the machine.
As a known logarithmic function arithmetic method, the so called STL (Sequential Table Lookup) method is known to be suitable for a computing machine of a microprogram control type, and is efficient, especially, for a computing machine which doesn't have a high speed multiplier.
A known logarithmic function arithmetic unit using the STL method comprises a single barrel shifter and a single adder/subtractor and effects loop processes of the STL method under the microprogram control.
However, the known arithmetic unit suffers from the following problems.
When it is provided that b (b is an integer) clocks are required for processing one loop process of the STL, (n.times.b) clocks (n being an integer) are required for processing n loop processes of the STL to compute a logarithmic function. This means that it takes a long time for computing a logrithmic function.
Further, the arithmetic result is not of high precision, since for example, the number of significant digits are reduced.